[ RadSafe ] BEIR VII

[John Jacobus]

Dale,
Sure, you can say that 100 mSv causes a 1% increase in
cancer, but how reliable is that number, i.e., what is
the confidence level?  For one thing, the ACS data on
cancer rates is only a statistical sampling.  They
select various countries or cities, and consider the
cancer deaths and incidents based on age, sex, race,
smoking, etc.  Then they multply the rates across
whole states and regions in the country.  As a
snapshot of cancers it is interesting, but I don't
expect those numbers to correlate with the incidents
in my town, county or even state.  

--- Dale Boyce <daleboyce at charter.net> wrote:

> Hi all,
> 
> I periodically like to point out when discussions
> like these arise that if 
> you take American Cancer Society data on cancer
> death rates by state and 
> plot them versus the mean altitude of the state
> there is a strong 
> anti-correlation.  That is the higher you live (and
> therefore the higher 
> your probable background exposure) the lower your
> risk of dying of cancer.
> 
> This is not an argument for or against hormesis.
> Just that if low level 
> exposure is harmful, it is much less so than the
> other differences between 
> the high and low states, such as heavy industry and
> air pollution tend to be 
> more common at lower altitudes because of
> accessibility to heavy transport 
> methods. It also show that the death rates vary by
> +/-20 state to state from 
> the national mean. How can someone say with a
> straight face that 100 mSv 
> causes an increase of 1% in cancer?
> 
> Another thing that I like to throw in every once in
> awhile is that the 
> linear model was developed from high dose data.  (I
> never get any takers on 
> answering this one) At high doses RBE's and Quality
> Factors do not apply. 
> The average dose to an individual cell is the same
> whether from a 100 rads 
> (1 gray) of photons or for example neutrons.
> Therefore, if we take the 
> linear model to low dose it should only work for
> high LET radiation. Where 
> an individual cell receives a similar dose as at
> high dose. Just a much 
> smaller fraction of the cells are exposed. These
> last two sentences are 
> fundamental to the LNT hypothesis.
> 
> So for low LET radiation I would argue that the LNT
> model should fail 
> because both the average cellular dose, and the
> fraction of cells exposed is 
> smaller (once you reach a small enough dose). To me
> this would indicate that 
> (IF the LNT model is correct for high LET radiation)
> then the dose response 
> at low dose should go as something like the square
> of the low LET dose. I 
> usually say it in a different way. At low dose of
> low LET radiation you 
> should divide the LNT by the RBE/QF's of high LET
> radiation.
> 
> This also points to another problem with the LNT
> model. Since we don't use 
> the QF's at high dose what unit is the LNT linear
> in?
> 
> In an offline discussion awhile back with another
> RADSAFER we were 
> discussing this last point about not using QF's at
> high dose. It makes sense 
> from a microdosimetry standpoint, and seems to be a
> fairly commonly held 
> view.  However, neither of us could find a reference
> to support this. 
> Anyone know?
> 
> Another question. At 40 years post
> Hiroshima/Nagasaki the excess cancer 
> deaths in those populations was something like 250
> out of a cohort of 80,000 
> or so. Does anyone have the most current figure?
> 
> dale
> 
. . .

+++++++++++++++++++
"Every now and then a man's mind is stretched by a new idea and never shrinks back to its original proportion." -- Oliver Wendell Holmes, Jr.

-- John
John Jacobus, MS
Certified Health Physicist
e-mail:  crispy_bird at yahoo.com

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